Hot melt stenciling method and apparatus



April 1, 1969 v. E. PENMNGTON HOT MELT STENCILING METHOD AND APPARATUSsheet @f2 Filed OCT.. 21, 1965 ATTORNEYS April 1, 1969 v. E. PENNINGTONHOT MELT STENCILING METHOD AND APPARATUS sheet Filed 00T.. 2l. 1965 QSAn a Z0 ATTORNEYS United States Patent Oce Patented Apr. l, 19693,435,757 HOT MELT STENCILING METHOD AND APPARATUS Victor E. Pennington,1359 Northlawn NE., Grand Rapids, Mich. 49505 Filed Oct. 21, 1965, Ser.No. 499,725 Int. CL B411 13/06, 27/00 U.S. Cl. 101--124 5 ClaimsABSTRACT F THE DISCLOSURE Stencil printing of a normally solid, heatlluidizable substance using hot air conducted onto the substance on thestencil to iluidize it and allow it to be squeegeed through the stencil,and then cooling to solidify it; the hot air being passed throughswinging conduits movable with the stencil through a manifold to thestencil area.

This invention relates to stencil printing apparatus and methodsutilizing printing materials that are normally solid at roomtemperatures, and more particularly relates to a method and apparatusyfor stencil printing with a solvent-free substance of 100% solids.

Most printing, including stencil printing, is conventionally practicedby employing a uid ink of a finely divided coloring agent in a liquidsolvent or carrier. By printing is meant the broad concept of applyingan agent on a surface to form words, designs, colors, etc. This isnormally done on a sheet and therefore will be described with respectthereto. As is known, freshly printed sheets require a substantial timeAfor drying by evaporation of the carrier. The printed sheets must bekept separate during the drying process until drying is complete, toprevent olfsetting or smearing. This necessitates large, expensivedryers which require a great deal of space. The dryer must be constantlydriven to circulate the sheets. They must be supplied with substantialamounts of heat. Further, the freshly printed sheets cannot be handledfor a substantial period after printing is complete.

It is an object of this invention to provide a method and apparatus ofprinting with a normally solid printing agent, without a liquid solventor carrier, to effect printed sheets which are dry practically instantlywhen emitted from the printer.

Another object of this invention is to provide a practical method andapparatus of printing with a 100% solid type printing substance by theemployment of heat in a manner to achieve high speed, controlledprinting without overheating and scorching of any sheet portions, withuniform ink uidization.

Another object of this invention is to provide a stencil printing unitthat can employ the basic portions of a conventional stencil printer,yet usefully employ a normally solid type printing agent in a mannerenabling high production output without any drying oven, recirculator orother drying facilities.

These and several other objects of this invention will become apparentupon studying the following specification in conjunction with thedrawings in which:

FIG. 1 is a top plan view of the novel apparatus;

FIG. 2 is a side elevational view of the apparatus in FIG. 1;

FIG. 3 is an end elevational view of the apparatus;

FIG. 4 is an enlarged fragmentary sectional view taken on plane IV-IV ofFIG. 1; and

FIG. 5 is an enlarged fragmentary sectional view taken on plane V-V ofFIG. 1.

Referring now speciically to the drawings, the complete printingassembly there illustrated includes a basic stencil printing subassembly12 and a recirculating hot air supplying subassembly 14.

Stencil printing subassembly 12 includes a conventional supportframework 16 to be mounted on a floor surface, and supporting therein ashiftable stencil holder 18, a rotationally mounted, paper sheetclamping impression cylinder 20 suspended transversely n the center ofthe frame for cooperation with the stencil on stencil holder 18, and aconventional transverse squeegee apparatus 22 axially along cylinder 20.

The details of the impression cylinder 20 and its drive mechanism arepreferably like that shown in U.S. Patent No. 3,120,180 assigned to theassignee herein. Likewise the details of the squeegee assembly are notcritical, and may be like that shown in the noted patent, for example,or the equivalent.

Suitable drive mechanism (not shown), for example, like that in theabove noted patent, may be provided to revolve impression cylinder 20.Each sheet to be printed is clamped in conventional clamp mechanism 20of this cylinder, and subsequently released vafter printing. Stencilholder 18 is reciprocated back and forth over the length of the machineduring rotation of cylinder 20. This may Ibe done, for example, byhaving underside gear racks 18a and 18h meshed with spur gears 30a and30b mounted on the rotational shaft (FIG. 3) of compression cylinder 20to rotate therewith. Hence, the stencil support 18 is reciprocatedbetween its dotted line position (FIG. 2) at one end of the bed, and itsphantom line position (FIG. 2) at the opposite end of the bed. In sodoing, it passes the stencil over progressive portions of a sheet pulledaround revolving cylinder 20, to thereby printthe sheet when ink issqueegeed through the stencil. The sheet is then discharged on to asuitable support 36 where it can be removed.

According to the concept herein, normally solid printing agents areused. Heat is applied to temporarily iuidize them. Specifically,preheated recirculated air is ejected in a pattern onto the stencilholder from its periphery. This is done to enable normally solid,nonsolvent, printing or coloring agents to be squeegeed through theorices of the stencil onto the sheet. The solid ink, normally in apowdered form, lmay be applied to the stencil by any suitabledistributor, as by being ejected from a portion of the squeegee holder22.

The heated air is provided using recirculating subassembly 14. Thissubassembly is preferably mounted above the stencil printing apparatusby a plurality of four corner support legs 34a, 34h, 34e and 34d.Mounted on the upper portions of these legs, spaced above the stencilprinting subassembly is a thermally insulated plenum housing 36 forminga hollow internal chamber 36. Suspended beneath this plenum chamber is adownwardly, outwardly flared warm air collection hood 3=8. Mounted alongone side of housing 36 is a burner heater unit 40 which preferablyemploys combustible gas for a heat source. This discharges into a heaterspiral 42 -which receives dynamically flowing pressurized air through aduct 44 from a blower 46. Blower 46 is a centrifugal type, driven byelectrical motor 48 through shaft 49, belt 51, and shaft 50. Shaft 50 ismounted on suitable bearing pillow blocks 52 and 52a. Motor 48 ismounted on a base 56, and blower 46, with its shaft, is mounted on asupport 58. Both base 56 and support 58 are secured to a transverse beam60 convected between legs 34C and 34d.

Air is propelled 1by blower 46 through d=uct 44 into heater spiral 42,and heated by combustion products from heater 40 ejected through outlet`64 into plenum chamber 36.

The heated flowing air is conducted from this plenum chamber to thestencil area by downwardly depending swinging tubular conduits, shown tobe siX in number. These conduits, namely 70a, 7Gb, '700, 72a, 72b, 72Care open on the upper end into plenum chamber 36. The lower ends areopen to communicate to portions of a rectangularly shaped orificed hotair manifold 78. These ducts are arranged in a parallelogram and mountedwith upper and lower swivel joints to swing arcuately with horizontalreciprocation of stencil holder 18. Each of the tubular ducts is formedof two telescopically interilitted members to automatically rvary inlength as the tubes oscillate arcuately between the solid line positionand the phantom line position shown in FIGS. l and 2.

The swivel connections may take any of a variety of different forms,with one upper end swivel connection being shown in FIG. 4, and onelower end swivel connection being shown in FIG. 5. Referring to FIG. 4,tubular member 72a includes a hollow lball member 80a on its upper end,received in oriiiced socket member 36a formed in the plenum chamber 36and through its insulation 37. Corresponding oriliced joints iStb, 80C,81a, 81h and 81C are provided for the other tive telescopic conduits(FIG. l).

The lower end of this member shown in FIG. 5 includes an interfittingtelescoping member 72cm having a ball joint member 82a on its lower end,iitted Within hollow socket member `84a which is in direct communicationwith the rectangularly coniigurated, tubular manifold 78.

This tubular Imanifold has outlet orifices `9() or the equivalent allaround the inner peripheral portion thereof to eject the heated gasesacross the stencil surface throughout the entire area within theperipheral stencil support 18. The hot air therefore ows over thestencil S retained in this stencil support during the entirereciprocation of the stencil support. Hence, the hot air heats the solidcoloring agent applied to the stencil and uidizes it to enable thesqueegee assembly 22 to force the uidized material through the stencilon to the underlying surface, eg., of a stock of sheets being advancedby impression cylinder 20. Immediately after the sheet is printed andejected on discharge surface 36, it cools and the agent resolidities.Thus it can be handled directly without any drying process.

In order to utilize the heated air to maximum advantage, it isrecirculated through the system to be used again. More specifically, thewarm air ows up into hood 318, suspended lbeneath plenum chamber housing36. It is conducted into a recirculating duct 94 (FIGS. 1 and 3), havingan outlet 94 into the inlet of fan or blower 46. This partially heatedair is then recirculated by fan 46 through duct 34 and through theheater area into heat. The heated owing air then is forced through theplenum chamber and tubes to the stencil as previously described. Thetemperature of the air can be controlled with a thermostat sensor andcontroller '37 operably connected with heat supply 40. The particularselected temperature will vary with the type of printing agent employed.The temperature is that necessary to soften the normally solid agentsuiciently to enable it to pass through the stencil screen orificesunder the action of the squeegee.

The illustrated form of the invention is the preferred form. lIt hasbeen found that this heated gas and air process fworks excellently with100% solid printing materials. It achieves high speed stencil printingwithout drying being necessary. The individual sheets can be stacked oneupon another as they are discharged. No scorching of the sheets ormaterials printed occurs with this assembly. Printing is uniform and ofhigh quality. It is conceivable, however, that certain variations ofconstruction detail may be made in the preferred illustrated formwithout departing from the concept taught. Hence, the invention isintended to be limited only by the scope of the appended claims and thereasonable equivalents to those defined therein.

I claim:

1l. Apparatus for printing with a normally solid, heat iluidizableprinting substance comprising: stencil support means; squeegee meansoperatively adjacent one side of said stencil support means; stocksupport means operatively adjacent the opposite side of said stencilsupport means; reciprocating means causing relative movement betweensaid stencil support means and said squeegee means to force a Huidprinting substance through a stencil on said stencil support means to asurface on said stock support means; hot gas supply means; and hot gasconduit means from said source means to said stencil support means, andhot gas outlet means at said stencil support means to heat soli-dprinting substance on a stencil on said stencil support means andtemporarily render it liuid for printing through the stencil.

2. Apparatus for printing with a normally solid, heat fluidizableprinting substance comprising: a supporting framework; reciprocablestencil support means on said framework; squeegee means adjacent oneside of said support means and oriented transversely to the direction ofreciprocation of said stencil support means to be cooperative therewith;stock support means adjacent said stencil support means on the oppositeside thereof of said squeegee means; hot air supply means; hot airdistributing means adjacent said stencil support means and mounted toreciprocate therewith to heat solid printing substance applied theretoto a fluid state; and shiftable hot air conveyance means from said hotair supply means to said distributing means.

3. Apparatus for printing with substances that are nontluid at roomtemperature and uid at elevated temperatures, comprising: a supportingframework; generally horizontal stencil support means reciprocablymounted on said framework and adapted to peripherally support a stencilin a plane; squeegee means above and operatively adjacent to saidstencil support means, oriented transversely of the direction ofreciprocation thereof; stock support means below and operativelyadjacent to said stencil support means; hot air source means; anorificed, hot-air distributing, manifold means about said stencilsupport means, having outlet orifices oriented toward the upper surfaceof said stencil plane to heat and render uid a printing substance on thestencil; and hot air propelling and conduit means from said source meansto said distributing means.

4. The apparatus in claim 3 wherein said hot air source means includes aplenum chamber spaced above said stencil support means, and said hot airconduit means includes oscillating tubes extending from said plenumcharnber to said manifold means.

5. A method of printing with a stencil onto a sheet comprising the stepsof: providing a stencil screen and sheet thereunder; distributing ontosaid stencil screen a normally solid, heat uidizable printing substance;blowing hot gases across the entire screen and substance thereon fromthe peripheral portions thereof to temporarily render said substanceuid; passing a squeegee over said screen to force a portion of saidsubstance therethrough onto said sheet to print it; and cooling saidprinted portion to resolidifiy it.

References Cited UNITED STATES PATENTS l/1944 Pollard lOl-126 1/1956Welsh lOl-129 FOREIGN PATENTS 5/ 1959 Great Britain.

